Peristaltic pumps of the type known for use for the infusion of medical fluids, or for the removal of body fluids, are generally characterized by a length of flexible tubing which is disposed within an arc between a stator-like member and a rotor assembly. The rotor assembly is provided with a plurality of rollers which, upon rotation of the rotor assembly, successively pinch-off the tube and advance the location of the pinch-off so as to progressively advance the fluid within the tube at a rate determined by the rate of rotation of the rotor. Such pumps have the advantage of having a disposable element in the fluid flow path, in that the length of tubing in the pump may be replaced after each use, and casettes have been provided to facilitate the insertion and removal of such lengths of tubing. Patents illustrative of such constructions are U.S. Pat. Nos. 3,927,955, 4,256,437, and 4,187,057. Despite their advantages, such systems are also known to exhibit poor accuracy and reproducibility, require substantial power for operation (thereby making them relatively expensive and inappropriate for battery operation), be relatively complex and bulky in construction, and require a casette which, because it must support the tube along an arcuate path, is relatively elaborate, complex, and expensive.
U.S. Pat. Nos. 4,199,307 and 4,273,121 disclose linear casettes for medical infusion systems, the casettes comprising tubes having flexible portions which are engaged by movable bar members at three different locations to control flow of fluid through the tubes. The use of pressure bars is also disclosed in U.S. Pat. No. 3,083,647.
Other patents such as U.S. Pat. Nos. 3,229,643, 3,981,633, and 3,233,553 disclose pumps in which shafts and eccentrics are disposed internally rather than externally in relation to the flexible tubes. Other patents generally illustrative of the state of the art are U.S. Pat. Nos. 3,067,692, 2,722,893, 1,874,667, 2,414,355, and 2,249,806.